1. Field of the Invention
The present invention relates to a miniature three-dimensional contour scanner, which can be used in narrow space to perform non-contact measurements of the three-dimensional objects.
2. Description of the Prior Art
The non-contact three-dimensional contour measurement technology refers to the use of different methods to create a light source and project it onto the surface of the object, by means of the various light path principles and photo detector to catch the characteristic data of the object's surface. This technique can be roughly classified as the active type and passive type depending on the manner of light source projection.
With regard to the active type non-contact three-dimensional contour measurement techniques, the method is to project onto an object desired to be measured the specially designed structured light patterns, for example, light-dot-array, periodical sine waves, light beams, etc, or other meaningful patterns. And due to the variations of the curvature or depth of the object's surface contour, it will lead to the deformation of the structured fringe projected onto the surface of the object. Therefore, after capturing the images of the deformed patterns by utilizing appropriate method, the object's three-dimensional contour data can be analyzed based on the acquired information, and the analyzing principles include, for example, the triangulation measurement method and the phase shift interference method, etc. In addition, the passive type non-contact three-dimensional contour measurement technique refers to utilizing the optical image technique of capturing the required characteristic data of the object's surface under natural illumination.
In recent years, the research and development have been widely discussed concerning the three-dimensional contour size of the object captured at high speed and with the optical non-contact technique. Meanwhile, the various creative methods and patents are disclosed (for example, C, Zhang at el., U.S. Pat. No. 6,169,634; 5,953,137; 6,373,561, which have been incorporated herein for reference ). However, at present only few measuring tools are concerning particularly about the in s itu e nvironment of the three dimension space measurement, wherein the measurement is performed in a specifically narrow space (for example, in the system configuration body or in the mouth cavity of human body). The size and volume of the three-dimensional scanners presently available on market are too excessively voluminous, and it is not suitable for being used directly in the non-contact precision three-dimensional contour scanning in the narrow space.
The CEREC system (as disclosed per U.S. Pat. No. 6,263,234)is one of a few three dimension tooth-form scanning measurement system presently in the world performed in the cavity of the mouth. It utilizes the grating pattern structured light of the infra-red ray (invisible light) , projecting upon the tooth-form to be measured in the cavity of mouth by four light grating movements (the amount per movement is ¼ grating pitch interval). The camera of the system takes pictures every ¼ interval, and calculate the phase shifting differences based on the relations between the depth of the object to be measured and the fringe image deformation amount so as to obtain the three-dimensional size. Since the projection fringes of the system are fixed, therefore its measurement accuracy and scope are apt to be restricted concerning the measurement of the curve-surfaced object containing stepped surface.
Besides, other measurement systems generate light grating fringes using the computer LCD projection method, and it can simultaneously generate arbitrary grating fringes patterns of a plurality of sets of different colors, which is superior to the ordinary fixed projection light grating fringes and has designable structured light fringe patterns and uniform projection effect. But the quality of the projection light grating fringes of liquid crystal display projection method is not the best, and the size of LCD is too large to be integrated easily into the miniature three-dimensional probe.